This invention relates to a monolithically integrable power regulator circuit and, more particularly, to a circuit for supplying an effective constant voltage to automobile instrument gauges.
The standard approach of using a bi-metallic switch to control power applied to automobile instrument gauges is well known. However, the use of such a switch presents certain problems. First, the opening and closing of the bi-metallic switch produces RF noise which may manifest itself as static in an automobile radio or stereo system. Secondly, it is not uncommon that the contacts of the bi-metallic switch remain closed due to sticking, allowing excessive voltage to be applied to the instrument gauges, thereby damaging the gauges.
Since automobile gauges presently have a very low manufactured cost, it is highly desirable that these gauges continue to be employed. Therefore, any electrical analog to the standard bi-metallic switch must be compatible with existing gauges. Further, the electrical analog must be capable of supplying a constant output, notwithstanding the fact that the source (battery) voltage may vary substantially from the desired output. For example, it is not uncommon that the battery voltage varies between 8 and 16 volts.